I am going to refer to an old topic that I posted a while back

/forums/ultimatebb.php?ubb=get_topic;f=23;t=002100#000000

Updated Specs: I am rebuilding a 400 engine from a '73. It will be a 4bbl w/ the Summit 2801 cam. The car has 2.78 rear gears. I would like to switch to 3.23 gears in the rear end, but that is only if I have the time/money. My car will be a street/cruiser machine. I will not be taking it to the strip. But I want to be able to stomp on it when necessary.

I am trying to make a decision on what tranny would be best in my 69.

The car came with a TH350 in it, but it needs some work.

With the rise in gas, I've been contemplating going with an overdrive tranny, but I can't decide 1) if I should, and 2) what transmission if I do.

With 2.79 gears, what is the best transmission (3 speed or overdrive)?

With 3.23 gears, what is the best transmission (3 speed or overdrive)?

If an overdrive transmission is the way to go, which type? 2004R or 7004R? Since my orginal trany was a TH350, I don't think I would need to cut my driveshaft if I went to a 2004R. But, I am concerned that the 2004R will not be strong enough.

Ideas would be appreciated.

Thanks,
Thomas

400 Turbo is the way to go with either gear ratio. A 200R4 would need some help to take any punishment. The overdrive trans will cost you 10 times as much to get set up right. You will never make up the difference with gas mileage.
Jim

The TH350 isn't a bad trans. It's not as strong as the TH400, but eats less power doing its job. You can also get a wide variety of torque converters and shift kits for it.

I've beat the living heck out of a TH350 without failure, but wouldn't select it for drag racing. I have a TH400 in my 'bird, but don't use it to its full capacity.

You can save your money and freshen up your TH350, then spend the savings on gas.

Since you're running a fairly stock setup, you can run the 2.78 for economy. However, the 400 is not an economy engine. Over the course of two seasons I've averaged 11 mpg with 2.73 gears. You can get a little more performance with the 3.23 and lose a little economy.

I have a quotes in town for rebuilding a 2004R from the low end of $375-550 and the high end of $800. The guy at $375 even said he uses Borg Warner clutches. /shrug

I get the same quotes for rebuilding by TH350.

Where can I calculate what my final RPM @ 70 mph would be with either a 3-speed or a 4-speed overdrive?

the 200 can be built plenty strong for street use for not much more than a rebuilt th350. a well built 2004r can be had for less than $1K, and will handle 350hp+

if you are making large amounts of low end torque, and are drag racing, it may not be the best choice for strength.

the 200 can actually be built stronger than the 700 can, but for more money. the stock 700 is stronger than the stock 200. early, non-upgraded models of either are to be avoided.

you wont see any mileage increase unless you are on long 45mph+ roads.

IMO the main benefit of a 200 or 700 swap is to pick up low end torque. it's low gears are lower, and the rearend can be swapped even lower, and not wind out the engine on the highway. this was why i chose the 200 for my 6cy engine. i was able to up the rearend to some serious gears, and the .67 OD will maintain low highway RPM.

if you are on the highway all the time, the OD may pick up a little mpg for you, and if you want some more low end, the 2.74 or 3.06 1st gear can help there too.

if you are happy with the low end, and are not a commuter, stick with the th350. your rearend is high enough you wont see a lot of benefit from the OD, even switching to 3.23's.


rpm calculator

I have a 2004r on the end of a 455 in a 69 bird the rear end is a 4:11 the combination is good for street or strip. the overdrive is great on the highway. at around 70 mph i'm only at 2400 rpm. the 2004r works great for me

chris

I personally bought this tranny:

http://www.2004r.com/trans/level2.shtml

The reason for such a beefy tranny behind a mildly modified 350 is because I plan to drop a mild 455 into the Firebird in the future. I wanted something that would handle 450 HP - 450 lb/ft range.

You can follow this LONG thread about my 2004r purchase with a parts/price breakdown:

/forums/ultimatebb.php?ubb=get_topic;f=23;t=001778#000010

I really like this tranny. Going from a 2 speed to a 4 speed with 2.78 rear gears was amazing. I can't believe the low-end I have now. Now I wish I had some 3.55 gears to go with the OD. I find I don't use the OD, I keep it in DRIVE, unless I'm going over 70 MPH. I think with a gear change I would use the OD more often. There's always something!

G.J.
68 350 Coupe (with the OTHER 4 spd)

Thomas,
If you get down to choosing between the 350 and 400 the 400 will last and the 350 may not. I have to admit that I put my cars through a lot. Having said that, I have burned up a few 350's. 400's are bullet proof. I guess it depends on how you drive or if you feel like changing trannies out after a good flogging.
Jim

Hey Thomas...

For your application, and from what you mention it's intended use. I think with the 2:79 gears would be best suited for the TH350/TH400 (obviously the easiest would be the 350, you wouldn't have to change drive shafts and crossmembers etc..)

For the 3:23 or better gears, the TH400 or the 200R would be the best choice.. especially if you do any long cruises... say down to hook up with all the Huston Area guys at some point!

But any of the 3, I don't think you could go wrong with, and you may not be able to fully take advantage of the 200R in the long run? So decide how you will use it (or abuse it) and then weigh out the cost difference, especially if you have to change crossmembers and drive shafts and other parts...

I have a 455/TH400, and it's just fine with my 2:76 gears but I'll be changing to 3:08, and that should be right where I'll want my little cruiser.

Brett - 67 Drop Top 455!

A well built T-350 with a shift kit will be fine in a street cruiser, a T-400 if you want to race alot. The 350 will be lighter, has a lower 1st gear & does not eat up as much HP to run. Also can use your old driveshaft & crossmember.

Steve